Preparation of pyrazinoylguanidines from pyrazinoylureas



Patented Nov. 10, 1970 3,539,569 PREPARATION OF PYRAZINOYLGUANIDINES FROM PYRAZINOYLUREAS Roger J. Tull, Metuchen, and Peter I. Pollak, Scotch Plain, N.J., assignors to Merck & Co., Inc., Rahway, NJ., a corporation of New Jersey No Drawing. Filed Aug. 21, 1968, Ser. No. 754,451 Int. Cl. C07d 51/76 U.S. Cl. 260-250 11 Claims ABSTRACT OF THE DISCLOSURE A process is described for the preparation of (pyrazinoyl)guanidines which comprises the treatment of a (pyrazinoyl)urea with a guanidine. The products have utility as diuretic and/ or natriuretic agents.

This invention is concerned with a novel process for the preparation of (3,5-diamino-6-halopyrazinoyl)guanidine compounds which possess useful diuretic properties but more importantly they selectively enhance the excretion of sodium and chloride ions while suppressing the excretion of potassium ions. The products prepared by the novel process of this invention are especially useful in the treatment or the management of edema and other abnormalities resulting from the retention of excess quantities of sodium and/ or fluid by the animal organism.

The novel process of this invention involves the reaction of a (3,S-diamino-6-halopyrazinoyl)urea, I, with a guanidine, II, to give the desired (3,5-diamino-6-halopyrazinoyl)guanidine product, III. This novel process represents a simple and economical method by which an important group of diuretic and/or natriuretic products can be produced.

The reaction comprises treating a (pyrazinoyl)urea with an excess of a guanidine in a polar nonhydroxylic solvent such as dimethylformamide, dimethylsulfoxide, dimethylsulfone or tetramethylurea at a temperature from about 50-100" C. for from to about 12 hours. The mixture is then treated with an excess of a dilute mineral acid such as hydrochloric acid in order to precipitate the (pyrazinoyl)guanidine as the acid addition salt which is collected and purified as the salt or is converted by standard techniques to the free base. The guanidine in the above reaction is conveniently formed in situ from one of its salts such as the hydrochloride by adding to the reaction mixture an alkali metal alkoxide such as sodium methoxide, sodium ethoxide, or the corresponding potassium alkoxides. This process can be illustrated by the following reaction scheme:

atoms and particularly the allyl, propargyl or 3-pentenyl and the like, or a lower(cycloalkylalky1) group advantageously having from 4 to 8 carbon atoms such as cyclopropylmethyl, cyclopentylmethyl, cyclohexylmethyl, cyclohexylethyl, cyclopropylethyl and the like; R represents hydrogen, lower alkyl advantageously having from 1 to 5 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, amyl, or any of the branched 4 or 5 carbon alkyl groups, or substituted lower alkyl groups having from 1 to 5 carbon atoms and particularly those containing hydroxy or a heterocyclic substituent such as the pyridyl substituent or a phenyl substituent, the phenyl-lower alkyl advantageously having an alkyl moiety of 1 to 2 carbon atoms and the phenyl moiety being either unsubstituted or substituted with 1 or more halogen (preferably chlorine, bromine, fluorine), lower alkyl (having 1 to 2 car bon atoms) and lower alkoxy (having 1 to 2 carbon atoms) groups; R advantageously is hydrogen, lower alkyl having 1 to 5 carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, amyl or any of the branched 4 or 5 carbon alkyl groups, phenyl-lower alkyl wherein the alkyl moiety advantageously has from 1 to 2 carbon atoms and the phenyl moiety being either unsubstituted or having one or more substituents selected from halogen (advantageously chlorine, bromine, fluorine), lower alkyl (advantageously having from 1 to 2 carbon atoms) and lower alkoxy (having 1 to 2 carbon atoms) groups; when R and R are each lower alkyl, they can be linked together to form a cyclic structure with the nitrogen atom to which they are attached, thereby forming a group having the structure 1\:T ((:3H)2x wherein x preferably is one of the numerals from 4 through 7 thus yielding, for example, the l-pyrrolidinyl group.

The (3,S-diamino-G-halopyrazinoyl)ureas used as the starting material in the novel process of this invention can be prepared according to the following reaction scheme:

The process comprises dissolving cyanamide in an anhydrous lower alkanol such as methanol, ethanol or propanol containing approximately an equivalent amount of an alkali metal such as sodium or potassium. After one-half to one hour at a temperature between ambient and reflux, solid pyrazinoic acid ester, IV, is added and the mixture is refluxed for an additional 2 to about 24 hours during which time a solid separates. This is collected by filtration, dissolved in water and the solution is made slightly acid by addition of an acid such as hydrochloric, hydrobromic, sulfuric, acetic, propionic or the like. Purification by re crystallization provides the intermediate (pyrazinoyl)- cyanamide, V.

The (pyrazinoyl)cyanamide is converted directly to the (pyrazinoyl)urea, 'III, by suspending the (pyrazinoyl)- cyanamide in dilute aqueous mineral acid such hydrochloric, hydrobromic, sulfuric acid or the like of from 3 to about 10 N in strength, preferably about 6 N and agitating the suspension until conversion to the (pyraz inoyl)urea is complete, that is from about 20 to about 30 hours at ambient temperature. The reaction can be for twenty-four hours. The (3,S-diamino-6-chloropyrazinoyl)urea is collected by filtration, washed with water and dried to yield 0.22 g., M.P. 300 C. Further purification is accomplished by recrystallization from methyl alcohol, M.P. 300 C.

conducted at temperatures between about 5 to 100 C., 5 Analysis.Calc. for C H ClN O (percent): C, 31.24; however, temperatures below ambient prolong the re- H, 3.06; N, 36.44. Found (percent): C, 31.25; H, 3.36; action time unnecessarily and temperatures above am- N, 36.28. bient lead to undesirable side reactions. When conver- Step C: Preparation of (3,5-diamino-6-chloropyrazinsion is complete, the product is isolated by filtration 0y1)guanidine.A mixture (3,5-diamino-6-chloropyrazand recrystallization. 10 in0yl)urea (0.1 mole) in 120 ml. of dimethyl formamide The examples which follow demonstrate the preparais treated with guanidine hydrochloride (0.5 mole) and tion of the (pyrazinoyl)cyanamide and the (pyrazinoyl)- sodium methoxide (0.45 mole). The mixture is stirred urea intermediates as well as the process of this invention at 70 C. under nitrogen for 8 hours, cooled to 40 C. by the preparation of several (pyrazinoyl)guanidines. l5 and treated with 360 ml. of 1.5 N hydrochloric acid. It is to be understood that the invention is not limited The mixture is cooled to 5 C. for 1 hour and the to the reagents and conditions employed in the specific (3,5 diamino-6-chloropyrazinoyl)guanidine hydrochloexamples but extends to reasonable variations thereof ride is collected by filtration, washed with 1.5 N hydrocognizable to those skilled in the art. chloric acid and air dried. This material is converted to the free base by dissolving it in water and adding EXAMPLE 1 a slight excess of sodium hydroxide slowly with stirring. more razino 1 Han-din The precipitated (3,5-d1am1no 6 chloropyrazinoyl)- 1 ml 6 py y )g 1 e guanrdlne is collected by filtration, washed well with Step A: Preparation of (3,5-diamino-6-chloropyrazinwater and air dried, M.P. 240.5241.5 C. oy1)cyanamide.-Cyanamide (13.6 g., 0.324 mole) is dis- The following table identifies other products prepared solved in a solution of sodium (7.6 g., 0.324 mole) in by the process of this invention. The method employed absolute methanol (525 ml.). This solution is refluxed for preparing these compounds is substantially that defor one-half hour and methyl 3,S-diamino-6-chloropyrazscribed in Example 1, steps A to C, with the variainoate (22.0 g., 0.108 mole) is added. Refiuxing is contions in solvents and temperatures described previously, tinued for twenty-four hours and the solid that separates 00 comprising the reaction of the appropriate methyl 3- during this time is collected by filtration. The solid is a amino-S-NR R -6-halopyrazinoate with an alkali metal dissolved in warm water (750 ml.), treated with desalt of cyanamide to form the corresponding pyrazinoylcolorizing carbon and filtered. The filtrate is acidified cyanamide which is then treated with an aqueous mineral to congo red paper by the addition of dilute hydroacid to form the (pyrazinoyl)urea. Treatment of the chloric acid and the (3,S-diamino-6-chloropyrazinoyl)- r (pyrazinoyl)urea with a 1-R -1-R -guanidine provides the cyanamide that precipitates is collected and dried, yield 1 (3-amino-5-NR R -6-halopyrazinoyl)-3-R -3-R -guani- 11.5 g. (50% yield), M.P. 330 C. dine end products. The reactants as well as the products Step B: Preparation of (3,S-diamino-6-chloropyrazinare identified in the table; the variables R R R oyl)urea.3,5 diamino-6-chloropyrazinoyl)cyanamide and R in the starting materials are not changed by (0.50 g.) is suspended in dilute hydrochloric acid (10 ml., the reaction conditions employed and remain unchanged 6 N) and this mixture is stirred at room temperature in the end-product produced and identified in the table.

N t N N -NHz NaHNCN N NHa e R R l -CO2CHa CNHCN halo halo (H) IEIzbl-C-NHR a R2 R2 N (fi-NH("JNH2 \N (||JNHCN halo 0 0 halo 0 M.P. C. R1 R1! R4 R5 of end prodi izi )1 H H H H 232. 5-235.5 H H 011 H 252-254 H H CHa- CH3' 277 H H C2H5- 02H5 265 H H CH CHz- 274.5

11 H -CH;CH;OH H a 228. 5-229. 5 H H -om 215-216 H H CH1@ H 220-223 See footnotes [at end of table.

- M.P. 0. (dec.) Example Halo R1 R2 R4 R! of end product;

10 01 H H -oH2--F H 216-219. 5

11 ..m H H -OHz-CH:1 H 210-212 12 01 I H H -CHzOCHa H mas-179.5

13 01---- H H -CHzCH3 H 220-222 I CH3 5 H H CH@ H 152-160 H H -OHzCHz- H 219-221. 5

H H -CH2 H 280. 5-283. 6

H iC H1- cH,- H 300 H iCsH1- CHa- CH3 238. 5-240 H 1o3H7- CHCH2OH H 6 185-186 H iC H CHQQ H 200. 5-204. 5

H CH2CH=CHz H H 213-214 H CH2OH=OH2 CH3 CH3- 213-215 H HC4H9 H3- CHa- 187.

H -CH2 H H 220-221. 5

CH3- CH3- H H 216-217 CH3 C2H5 H H 229-230 OH3 nC H1- H H 214-215 cmio3H1- H H 207-208 CHa- 1CaH1- a- (3112- 209-211 CgHa- 02H5- CH3 CH3" 212-314 1 As free base unless otherwise noted. 2 H01 monohydrate. a Hol. 4 21101. 5 H01 hemihydrate.

What is claimed is: 1. A process for the preparation of 1-(3-amino-5-NR R 6-chloropyrazinoyl)-3-R -3-R -guanidines of formula wherein halo is selected from the group consisting of chloro and bromo; R is selected from the group consisting of hydrogen; lower alkyl, lower alkenyl and lower(cycloalkylalkyl); R is selected from the group consisting of hydrogen, lower alkyl, lower alkenyl and C -cycloa1ky1- C -a1kyl; R is selected from the group consisting of hydrogen, lower alkyl, hydroxy-lower alkyl, phenyl-lower alkyl, (halo-phenyD-lower alkyl, (lower alkyl-pheny)- lower alkyl, (lower alkoxyphenyD-lower alkyl, and pyridyl-lower alkyl; R is selected from the group consisting of hydrogen, lower alkyl, and phenyl-lower alkyl, (halophenyl)-lower alkyl, lower-(alkylphenyl)alkyl, lower- (alkoxyphenyl)alkyl; which comprises the treatment of 1- (3-ami11o-5-NR R -6-chloropyrazinoyl)urea of formula wherein R and R are as defined above, with a 3-R -3-R guandine of formula wherein R and R have the meanings assigned above in a non-hydroxylic polar solvent.

2. The process as claimed in claim 1, wherein the solvent is dimethylformamide.

3. The process as claimed in claim 1 wherein R and R are each lower alkyl and R and R are as defined therein.

4. The process as claimed in claim 1, wherein R and R are each hydrogen and R and R are as defined therein.

5. The process as claimed in claim 1, wherein R R R and R are each hydrogen, thus yielding (3,5-diamino- 6-chloropyrazinoyl) guanidine.

6. The process as claimed in claim 1 wherein R and R are each lower alkyl and R and R are as defined therein.

7. The process as claimed in claim 1 wherein R and R are each lower alkyl and R and R are each hydrogen.

8. The process as claimed in claim 1 wherein R and R are each methyl and R and R are each hydrogen, thus forming (3-amino-5-dimethylamino-6-chloropyrazinoyl)- guanidine.

9. The process as claimed in claim 1, wherein R is hydrogen, R is lower alkyl, and R and R are as defined therein.

8 10. The process as claimed in claim 1, wherein R is hydrogen, R is lower alkyl, and R and R are each References Cited hydwgen- NITED STATES PATENT 11. The process as claimed in claim 1 wherein R is U S hydrogen, R is methyl and R and R are each hydro- 5 3300 494 1/1967 Cragoe 260 250 gen, thus forming (3-arnino-5-methylamino-6 chloropyrazinoynguanidine NICHOLAS S RIZZO, Primary Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION nun: 110. 69 Dated 11/10/70 Inventor) Roger J. Tull and Peter I. Pollak It in certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected a sham below:

In column 1, line 64 formula III, that portion of the formula reading /R -NH-CN should read -NH-CN s H s NH In column 2, line 33, the formula reading 1" A (p 2X should read -N CH In column 6, line 59, Claim 3, delete the entire line and in its place insert -are each hydrogen and R and R are as defined therein.

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